The tropics are quiet

By: Dr. Jeff Masters , 1:11 PM GMT on September 06, 2009

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Considering that this is historically the peak week of the Atlantic hurricane season, the tropics are quiet. There is an area of disturbed weather in the middle Atlantic (95L) that NHC has been mentioning in their Tropical Weather Outlook the past day, but this disturbance is entering a region of high wind shear and is not a threat to develop.

A strong tropical wave with plenty of rotation is emerging off the coast of Africa this morning, and this wave is a good candidate to show some development this week as it heads west-northwest over the Atlantic. The wave is under about 15 knots of wind shear, and is being developed by several models, including the GFS and ECMWF. However, the models show that this new wave will be pulled northwestward by a strong trough of low pressure this week, and it appears unlikely that the wave will make the long crossing of the Atlantic necessary to threaten any land areas. Another wave with plenty of spin will emerge from the coast of Africa two days from now, and will also have a chance to develop.


Figure 1. Morning satellite image of 95L and a new tropical wave with potential to develop, emerging from the coast of Africa.

An area of concentrated thunderstorms has developed off the North Carolina coast in association with the remains of an old cold front. This system is under about 20 - 30 knots of shear, and is not tropical. However, it will bring heavy rain just offshore of North Carolina's Outer Banks today as it slides north-northeastward along the coast.

I'll have an update Monday.

Jeff Masters

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Quoting 10Speed:


My estimate is 5% at the most.


what did you expect...its the GOM, anything in the GOM automatically gets a higher chance than anywhere in the Atlantic, even if you dont like tropical systems.

Gulfcasters
Member Since: July 24, 2005 Posts: 407 Comments: 19076
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1741. 10Speed
Quoting IKE:
Looks like 96L will be Fred.

If something pops in the GOM it would be Grace. I would put the odds of something forming and named in the GOM at 25-30%, right now.


My estimate is 5% at the most.
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But I'm not discounting anything in the GOM as with Claudette and Humberto, just gotta watch in the meantime.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
The title of the blog makes no since now that we have these to storms.
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Tough one, Can you explain why there may be a decrease in shear in the GOM this weak, considering there is currently a shortwave trof over LA? TIA.
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I hope 96l/Fred is a fish. The ECMWF spins it up quickly then just before it hits 40w it looks to build the ridge back in over it and turn it wsw. Hopefully the other storm they show makes enough of a weakness in time.
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Cyclogenesis in the GOM seems unlikely at this moment.

Member Since: July 24, 2005 Posts: 407 Comments: 19076
1735. 10Speed
Seeing that all the big wheels are off celebrating Labor Day today and have left a peon in charge (isn't it suppose to be the other way around?)... I officially declare Sept. 7, 2009 as the last day of the 2009 hurricane season.
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Quoting Weather456:
Good Morning and Happy Labour to you guys

Yea we spell Labour the British way here..

Tropical Update


Excellent to see... superfluous vowels should never die!
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Guess we're looking for 'It might be turning into a TD'... usually the signal it's getting upgraded.

Possibly at 2.

And yeah, happy "Labor" Day to all you Americans... :)
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Good Morning and Happy Labour to you guys

Yea we spell Labour the British way here..

Tropical Update
Member Since: July 24, 2005 Posts: 407 Comments: 19076
96L still looking good and I see it has been upgraded to code red.
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1730. IKE
Looks like 96L will be Fred.

If something pops in the GOM it would be Grace. I would put the odds of something forming and named in the GOM at 25-30%, right now.
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Quoting homelesswanderer:
Oh for crying out loud! If we even get brushed by something tropical on the 13th that would be 3 years in a row. Best I can tell if anything came this way it would be the 14th but still what are the odds? Lol. Geesh.


Peak of the season, I'd imagine the odds are pretty high...
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Quoting Ameister12:
Good morning and Happy Labor day, everyone!


Good morning. :)
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1727. WxLogic
Quoting homelesswanderer:


Good morning. :)


:) Morning...
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Oh for crying out loud! If we even get brushed by something tropical on the 13th that would be 3 years in a row. Best I can tell if anything came this way it would be the 14th but still what are the odds? Lol. Geesh.
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Good morning and Happy Labor day, everyone!
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i saw erica lower parts slam into hispanola a few days ago. there was banding north of the island. what was left behind in leftover opinion was a mid level swirl which played havoc near prico for a day or so
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1723. WxLogic
I see you guys are discussing the possible low development in the GOM the NAM has been hinting at for quite sometime.
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Quoting WxLogic:
Good morning...


Good morning. :)
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1721. WxLogic
Good morning...
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NAM 06Z high resolution 10M wind
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Morning Storm. :)
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Quoting IKE:


That's September 14th. I would say no.


Ok. Thanks. Just not usually like them to spin something up like the CMC is famous for. And everyone last night didn't seem to think the low there now would have time to make it.
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1716. IKE
Quoting homelesswanderer:
So is the low off NC the storm the EURO spins up on that model Future just posted?


That's September 14th. I would say no.
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So is the low off NC the storm the EURO spins up on that model Future just posted?
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1714. IKE
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I guess I should explain my last post. Houston considers itself SE TX. But the SE TX in the Lake Charles discussion is just about everything between Houston and the Louisiana border. I didn't know til recently Houston was SE TX. Lol.
I'm not from here what can I say? :)
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1712. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT MON SEP 7 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE ASSOCIATED WITH A STRONG TROPICAL WAVE
IS LOCATED ABOUT 200 MILES SOUTH-SOUTHEAST OF THE SOUTHERN CAPE
VERDE ISLANDS. SHOWER AND THUNDERSTORMS ACTIVITY ASSOCIATED WITH
THIS SYSTEM IS SHOWING SIGNS OF ORGANIZATION. CONDITIONS APPEAR
FAVORABLE FOR THE LOW TO DEVELOP INTO A TROPICAL DEPRESSION LATER
TODAY OR TONIGHT AS IT MOVES WEST OR WEST-NORTHWESTWARD AT NEAR 20
MPH. LOCALLY HEAVY SHOWERS AND STRONG GUSTY WINDS ARE LIKELY OVER
THE SOUTHERN CAPE VERDE ISLANDS TODAY. THERE IS A HIGH CHANCE...
GREATER THAN 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

A TROUGH OF LOW PRESSURE LOCATED JUST OFF THE COAST OF NORTH AND
SOUTH CAROLINA IS PRODUCING AN AREA OF DISORGANIZED SHOWERS AND
THUNDERSTORMS. UPPER-LEVEL WINDS ARE EXPECTED TO REMAIN
UNFAVORABLE FOR SIGNIFICANT TROPICAL CYCLONE FORMATION AS THIS
SYSTEM MOVES NORTH-NORTHEASTWARD. THERE IS A LOW CHANCE...
LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BROWN
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1711. IKE
Quoting futuremet:
THIS FEATURE MAY BE ASSOCIATED WITH A PART OF THE REMNANTS OF FORMER
TROPICAL STORM ERIKA.


Trying to sneak up on us I see


LOL....Erika....
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Quoting futuremet:
THIS FEATURE MAY BE ASSOCIATED WITH A PART OF THE REMNANTS OF FORMER
TROPICAL STORM ERIKA.


Trying to sneak up on us I see


Lol. I was fixing to say Erika's going to make landfall after all.
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THIS FEATURE MAY BE ASSOCIATED WITH A PART OF THE REMNANTS OF FORMER
TROPICAL STORM ERIKA.


Trying to sneak up on us I see
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FWIW From Houston...

ALL OF THE MEDIUM RANGE MODELS FORECAST A RATHER DEEP LONGWAVE
TROUGH TO FORM OVER THE PLAINS/GREAT LAKES REGION NEXT WEEKEND.
THE ENSEMBLE MEAN KEEPS THE TROUGH FURTHER EAST THAN THE
GFS/ECMWF. FLOW ALOFT WILL SHIFT TO A NORTHERLY DIRECTION BY
SATURDAY WITH WEAK DISTURBANCES IN THE FLOW ALOFT LIKELY TO
ENHANCE CONVECTIVE POTENTIAL NEXT WEEKEND. WHILE NOT A MAJOR
FRONT...AT LEAST A WEAK COLD FRONT IS LIKELY TO REACH SE TX BY
SUNDAY AND STALL OVER OR JUST SOUTH OF THE AREA...SERVING AS A
FOCUS FOR CONVECTIVE DEVELOPMENT. HAVE BLANKETED 30 POPS AREA WIDE
FOR NOW. TEMPS SHOULD MODERATE TO NORMAL LEVELS THIS PERIOD.

Going east to Lake Charles...

DRIER AIR WILL CONTINUE TO SPILL INTO THE REGION ON TUESDAY FROM
THE NORTH WITH A REPEAT OF TODAY EXPECTED. SOUTHERLY WINDS WILL
AGAIN RETURN LATE TUESDAY WITH A DEEPER MOISTURE PROFILE BUILDING
INTO SE TX AND SRN LA FOR WEDNESDAY. CHANCES FOR SHOWERS WILL
INCREASE ON THURSDAY THROUGH SATURDAY INTO SUNDAY AS GULF MOISTURE
AND DAYTIME HEATING WILL ENHANCE AND SUPPORT AFTN STORM
DEVELOPMENT
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1707. IKE
From Key West morning discussion....

"SHORT TERM (TODAY THROUGH WEDNESDAY)...
A RATHER COMPLEX PATTERN WILL EVOLVE ACROSS THE REGION DURING THE
SHORT TERM PERIOD. INITIALLY...IT APPEARS THAT THE SOUTHERN END OF
THE LOW LEVEL TROUGH NOW JUST EAST OF SOUTH FLORIDA WILL MIGRATE
SLOWLY WESTWARD TOWARD THE KEYS TODAY. TONIGHT THROUGH WEDNESDAY...
A MORE SUBSTANTIAL LOWER TO MID LEVEL CYCLONIC CIRCULATION IS PROGGED
TO TAKE SHAPE OVER THE FLORIDA STRAITS...AND SLOWLY DRIFT WESTWARD.
THIS FEATURE MAY BE ASSOCIATED WITH A PART OF THE REMNANTS OF FORMER
TROPICAL STORM ERIKA.
MEANWHILE AT UPPER LEVELS...SHORTWAVE RIDGING
WILL REMAIN OVERHEAD TODAY...THEN WILL BE DISPLACED SOUTH OF THE KEYS
TONIGHT AND TUESDAY BY THE TROUGH PROGRESSING EASTWARD FROM THE NORTH
CENTRAL GULF REGION.

FOR TODAY...CONTRADICTORY INDICATORS COME INTO PLAY REGARDING PRECIP
CHANCES. THE PROXIMITY OF THE SURFACE TROUGH SHOULD HELP TO ENHANCE
LOW LEVEL CONVERGENCE JUST TO OUR EAST...AND NORTHEAST STEERING FLOW
SHOULD HELP TO BRING MAINLAND ACTIVITY DOWN INTO OUR AREA...PERHAPS
ALLOWING FOR CLOUD LINE DEVELOPMENT AS WELL. ON THE OTHER HAND...THE
DRY AIR EVIDENT IN WATER VAPOR LOOPS AND PRESENT ON THE SUNDAY
EVENING KEY WEST SOUNDING WILL NEED TO MOVE AWAY OR BE MODIFIED...AND
RELATIVELY WARM/STABLE UPPER LEVELS DUE TO THE PRESENCE OF THE
SHORTWAVE RIDGE WILL NOT BE AN ENHANCING FACTOR FOR PRECIP. BEST
GUESS IS THAT WE SHOULD SEE SOME CONVECTION THIS AFTERNOON...BUT THE
BULK OF IT MAY NOT REACH THE KEYS UNTIL THIS EVENING...AND WILL NUDGE
POPS FOR TODAY DOWN SLIGHTLY TO 40 PERCENT.

TONIGHT THROUGH WEDNESDAY...THE LATEST GUIDANCE INCLUDING THE NEW
ECMWF IS IN DECENT AGREEMENT...WITH A WEAK LOWER/MID LEVEL
CIRCULATION EMERGING FROM CUBA AND DRIFTING SLOWLY WEST NORTHWEST
THROUGH THE STRAITS.
THIS SHOULD PROMOTE LOW LEVEL CONVERGENCE...AND
ALSO BRING ENHANCED TROPICAL MOISTURE UP INTO OUR AREA. THE MID AND
UPPER LEVELS SHOULD BECOME MORE FAVORABLE AS WELL...WITH THE
SHORTWAVE RIDGE EXITING TO OUR SOUTH ALLOWING FOR SLIGHT COOLING
ALOFT. WOULD GENERALLY EXPECT ABOVE NORMAL PRECIP CHANCES THROUGHOUT
THIS PERIOD. LIKELY POPS COULD BE NEEDED AT SOME POINT...BUT UNTIL WE
HAVE A BETTER IDEA OF THE EVOLUTION OF THIS RATHER COMPLEX
SCENARIO...WILL CONTINUE WITH HIGH END CHANCE POPS OF 50 PERCENT...
ALONG WITH MORE CLOUD COVER THAN USUAL.

.LONG TERM (WEDNESDAY NIGHT THROUGH SUNDAY)...
THE WEAK LOWER TO MID LEVEL TROUGH SHOULD BE PASSING INTO THE
SOUTHEASTERN GULF WEDNESDAY NIGHT AND THURSDAY...LEAVING THE KEYS
WITHIN A RATHER MOIST SOUTHEAST/SOUTH FLOW REGIME. THIS PATTERN
SHOULD STILL BE FAVORABLE FOR CONVECTION...PERHAPS ORIGINATING FROM
NORTHWARD MOVING OUTFLOW BOUNDARIES COMING OFF CUBA...AND WILL BUMP
POPS UP TO 50 PERCENT FOR THOSE PERIODS.

THURSDAY NIGHT THROUGH THE WEEKEND...DEEP LAYERED TROUGHING OVER THE
EASTERN CONUS WILL GRADUALLY LIFT OUT...WHILE ANOTHER MORE INTENSE
TROUGH DEVELOPS OVER THE CENTRAL/NORTHERN PLAINS STATES. THIS SHOULD
ALLOW FOR THE SUBTROPICAL RIDGE TO BUILD ACROSS FLORIDA STARTING
FRIDAY...WITH THE RIDGE BECOMING QUITE STRONG OVER SOUTH FLORIDA
DURING THE WEEKEND. MEANWHILE...THE LOW LEVEL FLOW REGIME SHOULD
REMAIN FROM THE SOUTH ON FRIDAY...THEN BACK TO THE SOUTHEAST DURING
THE WEEKEND AS THE WESTERN ATLANTIC SURFACE HIGH NOSES INTO FLORIDA.
WILL CONTINUE WITH NEAR CLIMO 40 PERCENT POPS FOR THURSDAY NIGHT
THROUGH FRIDAY NIGHT. WILL LOWER POPS DOWN TO 30 PERCENT FOR SATURDAY
THROUGH SUNDAY...WHEN STRONG RIDGING AT ALL LEVELS SHOULD HELP TO
SUPPRESS CONVECTION VIA SUBSIDENCE."
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Quoting futuremet:


The NAM shows extending surface trough, with two separate lows trying to form. The models do not have good handle on where along the surface trough will dominant low form. The hybrid low will form next week by Texas.


Thanks Future.
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Quoting stormsurge39:
Are we looking at possible tropical storms or hurricanes?


I don't know

likely a storm
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Low number 1: extending surface trough.



Low number 2: low pressure system off Texas coast

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1702. IKE
Shear is 20 to 30+ knots in the northern GOM. Low shear of 10 knots is where that vorticity is at.....

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Quoting futuremet:


Yes...
Are we looking at possible tropical storms or hurricanes?
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Quoting stormsurge39:
Thanks, so GOM has potential for 2 tropical systems within a week?


Yes...
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Quoting IKE:


I hadn't looked at the vorticity map. Thanks...I see it now.


Claudette did the same thing...it showed up exactly like this, and developed well defined mid level circulation within 12hrs.
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Quoting futuremet:


Wednesday of this week and the middle part of next week.

Thanks, so GOM has potential for 2 tropical systems within a week?
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Quoting homelesswanderer:


I thought hey were 2 different things as well. The NAM was showing something farther east as well.


The NAM shows extending surface trough, with two separate lows trying to form. The models do not have good handle on where along the surface trough will dominant low form. The hybrid low will form next week by Texas.
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Two seperate features:



MODEL DIAGNOSTIC DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
227 AM EDT MON SEP 07 2009


GULF COAST/FLORIDA...
WHILE THE NAM HAS SHOWN REASONABLE CONTINUITY ALOFT WITH THIS
FEATURE DURING ITS PAST DAY OF RUNS...THE SURFACE LOW IT SPAWNS
NEAR THE NORTHERN CUBAN COAST WHICH MOVES TOWARDS FLORIDA IN A FEW
DAYS IS NEW ON THE 00Z RUN. THE GFS HAS SHOWN GOOD CONTINUITY
OVER THIS REGION DURING ITS PAST DAY OF RUNS. THE ECMWF HAS SHOWN
REASONABLE CONTINUITY ALOFT WITH THIS SYSTEM OVER ITS PAST COUPLE
DAYS OF RUNS...THOUGH ITS 12Z RUN SHOWED A NEW SURFACE LOW IN THE
SOUTHEAST GULF OF MEXICO BY THURSDAY MORNING. WHEN COMPARING THE
GUIDANCE...THE NAM IS AN EASTWARD/DEEP OUTLIER WITH THE LOW MOVING
THROUGH THE FLORIDA STRAITS AND WILL PREFER A 12Z OR 00Z UKMET/12Z
OR 00Z ECMWF COMPROMISE HERE WHICH LIES IN THE MIDDLE OF THE 12Z
MULTI-MODEL ENSEMBLE LOW ENVELOPE. ALONG THE NORTHERN GULF
COAST...THE 12Z CANADIAN USED ENERGY MOVING ACROSS NORTHERN MEXICO
TOWARDS THE REGION TO SPIN UP A STRONGER SURFACE LOW NEAR
LOUISIANA...WHICH HAS VIRTUALLY NO 12Z MULTI-MODEL ENSEMBLE
SUPPORT OR SUPPORT FROM ITS OWN 00Z RUN. WILL THEREFORE GO WITH
THE WEAKER CONSENSUS ALONG THE NORTHWEST GULF COAST.

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Quoting stormsurge39:
When will the window of oppurtunity be?


Wednesday of this week and the middle part of next week.

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Quoting futuremet:


The low the NOGAPS is showing is the surface in the East GOM that might develop. Look near eastern Texas, and you will signs of cyclogenesis.

A tiny patch of vorticiy is already showing up just north Cuba......wait a minute....this is the same thing that happened with Claudette.



I thought hey were 2 different things as well. The NAM was showing something farther east as well.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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